jan 2013 Flashcards
What is spooling an acronym for?
simultaneous peripheral operations on line
What are the uses of spooling?
allows sharing on a network
avoids delays / frees processor
allows jobs to be prioritised
avoids speed mismatch
What is spooling in the context of printing?
output data to disk drive/storage device
for printing at another time
examples of utility in an operating system?
anti virus
defragmenters
compressors
cleaners
Data security in an operating system?
use of passwords
access rights
encryption
role of memory management?
partitioning allocates memory virtual memory paging segmentation
What happens in lexical analysis?
strips out comments and white space replaces reserved words with tokens variable names stored for later use error messages output if necessary resulting tokens fed into syntax analysis
definition of token
a string of binary digits of fixed length
What happens during syntax analysis?
tokens checked to see if the rules of the language are being followed
errors detected are passed to the user
if no errors - goes to code generation phase
features of von nuemann
single control unit
program stored with data in the same format
one instruction at a time
definition and use of registers
location in the processor used for a particular purpose temporarly stores data allows very high access speeds allows frequent exchange of data
Role of the Current Instruction Register?
contains the instruction to be executed
splits instruction into component parts
holds opcode while its decoded
sends the address to the MAR for accessing data
sends address to PC for jump instruction
determines the type of addressing to be used
Describe a procedural language?
imperative language statements in blocks called procedures and functions program states what to do and how to do it statements in a specific order
What does BNF stand for?
Backus-Naur form
What is BNF used for?
defining terms unambiguously in a computer language
What are high level languages used for?
more complex programs problem orientated portable easier to maintain uses library routines
indirect addressing
uses addressing field as a pointer (vector)
… to the address to be used
increases the size of the address that can be used
allows a wider range of locations to be accessed
relative addressing
allows real address to be calculated by adding a base address
… to the operand
relative address is an offset
can be used for arrays/ branching
purpose of views of data
provides access to relevant data
… for a routine task
without the need to write code
can restrict data to confidential data
parts of an object diagram?
dotted lines - lifelines
arrows - messages
boxes - activation
